John Saunders (Mark Dightam) loses his pet mouse, Alice, on a school trip to the Tower of London.
Next day, on the underground, he turns yellow. With the help of Nick (short for ‘Electronic’) John learns about electricity and discovers that he can travel through a television set on electronic waves.
He flashes to the Tower at night to look for Alice but is arrested by beefeaters who are going to chop his head off.
John escapes by asking to watch TV as a last request and disappearing into the set.
Back home, Alice has returned and given birth.